Late MLB Player Oscar Taveras -- Cardinals Fan Gives Up Memorabilia Stash to Help Oscar's Family

The family of late Cardinals outfielder Oscar Taveras has some cash headed their way ... all thanks to a longtime fan who's auctioning off his treasured souvenirs.

Taveras got his first taste of the majors this season, but he made a huge impression on a Cards fan. TMZ Sports has learned the guy -- who wants to remain anonymous -- bought a bunch of Taveras memorabilia ... just one day before the 22-year-old died in a car accident.

We're told the items include -- Oscar's first home run ball, cleats from his first big league game, and a game worn post-season jersey ... all autographed and going up for auction.

We're told the fan decided to unload the merch through Goldin Auctions -- so he can donate all the profits to Oscar's family in the Dominican Republic. The auction will open on January 12th.